Re: OpRegion conflicts for Skylake LPSS

[Mika Westerberg]

On Sun, May 01, 2016 at 12:47:58AM +0200, Ben Gamari wrote:
> Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> writes:
> 
> > On Fri, Apr 29, 2016 at 09:30:27AM +0200, Ben Gamari wrote:
> >> Ben Gamari <ben@xxxxxxxxxxxxxxxx> writes:
> >> 
> >> > [ Unknown signature status ]
> >> > Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> writes:
> >> >
> >> >> On Tue, Apr 26, 2016 at 02:44:13AM +0200, Ben Gamari wrote:
> >> >>> 
> >> > snip
> >> >
> >> >>> It looks very much like these are describing the same device. Perhaps
> >> >>> the lpss driver should be binding to this ACPI node? Or perhaps this is
> >> >>> a firmware issue? Any guidance would be greatly appreciated.
> >> >>
> >> >> Can you send me full acpidump of that machine?
> >> >
> >> > It can be found at
> >> > https://github.com/bgamari/dell-e7470-dsdt/blob/master/acpi.log.
> >> >
> >> Did this provide any insight? Let me know if more information would be
> >> helpful.
> >
> > Sorry about the delay.
> >
> No worries.
> 
> > The GEXP device is most probably a GPIO expander that is connected to
> > one of the I2C buses. And it indeed looks to use directly the I2C host
> > controller registers so kernel rightfully complains about that.
> >
> > Are you able to run Windows on that machine? If yes, it would be nice to
> > know if the INT3446 I2C device is shown in the device manager.
> >
> I had the original SSD that came with the machine with the original
> Windows 7 installation intact. I popped it in and found no such device.
> I then updated to Windows 10 (albeit still booting with the legacy BIOS,
> not EFI) and found that once again there is no such device shown in
> device manager.

That's what I would expect. ACPI spec says that if there is an OpRegion
touching the same registers than PCI device the OS should not load any
driver for that device. I guess this is exactly what Windows does.

Linux does it also but it in addition it issues a scary warning which
might get users thinking there is something wrong with their system.

> >> Also, is there a way to simply allow the driver subsystem to allow
> >> probing to proceed despite this resource conflict so that I can resume
> >> debugging my original input device issue?
> >
> > Try to pass "acpi_enforce_resources=lax" in the kernel command line.
> 
> Thanks, indeed this allows the driver to load. Unfortunately it didn't
> take long to encounter further issues.
> 
> The motivation for all of this is to get the touchpad into I2C mode, since
> currently it is merely exposed as a simple PS/2 device. Unfortunately it
> seems that even Windows 10 doesn't use the touchpad's I2C mode (although
> I suppose it's possible that this is guarded on UEFI boot; moreover
> Windows appears to have proper support for configurating this touchpad
> in PS/2 mode, which is unfortunately an ALPS devices).
> 
> Looking at the DSDT it seems that enabling the I2C interface may require
> the help of the embedded controller, the state of which is exposed in
> the DSDT through a mysteriously-named SDS1 field. It looks like this
> field could take on a number of values which identify a variety of
> different touchpads. Given that it looks like GPIO pin states may be
> determined by the value of this field I'm a bit reluctant to go fiddling
> around with it. 
> 
> I do wish that firmware weren't such a nightmare.

+1